The production of living sheep eggs

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Abstract
1. In the 1954–5 and 1955–6 breeding seasons, 117 ewes of the Border Leicester, Welsh Mountain and Suffolk breeds were used in order to investigate the effects of PMS treatments on (a) the length of the dioestrous cycle, (b) the number of ovulations per ewe, (c) the proportion of eggs which were cleaved, uncleaved or abnormal when recovered, and (d) the ability of fertilized superovulated eggs to develop normally.2. In the 1954 and 1955 anoestrous periods, ninety-four 2-tooth and mature ewes of mixed breeds were used in order to investigate (a) the proportion of ewes which could be induced to ovulate and exhibit oestrus as a result of treatment with progesterone and PMS, (b) the proportion of the mated ewes which had cleaved, uncleaved or abnormal eggs, and (c) the ability of fertilized eggs shed during anoestrum to develop normally up to the 21st day of pregnancy.3. Dioestrous cycles in untreated ewes were significantly shorter for Welsh Mountain than for Border Leicester ewes, and their length was not affected by the year in which they were measured. The first and second cycles of the breeding season tended to be shorter than the third cycle.4. The length of the dioestrous cycle was shortened by treatment of both Border Leicester and Welsh Mountain ewes with PMS. The average extent of this reduction was 0·6 days, and the effect was significant.